RU2529216C1 - Method of production of thin-film organic coating - Google Patents

Abstract

FIELD: nanotechnology.

SUBSTANCE: invention relates to a technology of nanomaterials and nanostructures, and can be used to produce thin-film polymeric materials and coatings used in sensing, analytical, diagnostic and other devices, and when creating the protective dielectric coatings. The method of production of thin-film organic coating of cationic polyelectrolyte comprises modification of the substrate, preparing the aqueous solution of cationic polyelectrolyte with the adsorption of polyelectrolyte on the substrate, washing, drying the substrate with the deposited layer. The substrate is used as monocrystalline silicon with roughness less than or comparable with the thickness of the obtained coating. To generate the negative electrostatic charge the substrate is modified in the solution of alkali, hydrogen peroxide and water at 75°C for 15 min. During the adsorption the substrate is illuminated from the side of the solution with light having intensity in the range of 2-8 mW/cm² and with wavelengths of the range of intrinsic absorption of silicon.

EFFECT: invention enables to reduce the roughness and thickness of the organic coating.

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Description

Technical field

The invention relates to the technology of nanomaterials and nanostructures and can be used to obtain thin-film polymeric materials and coatings used both in sensory, analytical, diagnostic and other devices, and when creating protective dielectric coatings.

State of the art

For applying thin-film organic coatings to substrates, methods such as Langmuir-Blodgett technology, centrifugation, chemical deposition, vacuum deposition, and layer-by-layer adsorption of charged organic molecules are widely used. Each method has its own advantages and disadvantages caused by both the technological features of the method and the structural features of organic molecules, for example, the existence of various conformations. This can affect the parameters of the coatings, such as their thickness, the thickness of one layer by area, and surface roughness.

A known method of manufacturing a polymer coating to protect the substrate of the optical information carrier, in which the disk-shaped form is filled with liquid organic (polymer) material, the material is cured, and then the resulting casting is removed from the mold (see RF patent for invention RU 2068200, IPC G11B 7/26 ) In the process of curing the organic material, the disk-like shape is rotated around its central axis at a constant speed from 100 to 17000 rpm. The known method allows to obtain a surface with a low roughness (0.01-0.05 μm), a thickness difference (± 10 nm) and a discontinuity (less than 3%) of the coating.

However, this method does not allow to obtain an organic layer of nanometer thickness, and is also limited to use exclusively for a disk-shaped substrate.

A known method of applying a carbon-containing film, including organic, on a substrate from the gas phase (see RF patent for the invention RU 2141005, IPC C23C 14/58, C23F 4/04). Further ion-plasma polishing etching reduces the surface roughness of the coated substrate. This method allows to obtain thin-film materials with a low roughness (6.5 A).

However, the carbon-based film required in this technology, which may also contain hydrogen, oxygen, fluorine, and nitrogen atoms, is deposited on top of the functional structure and leads to a change in the chemical composition of the surface. The carbon-containing coating uncontrollably changes the surface electrophysical properties (which are important when using the obtained structure for the deposition of functional groups from a solution) and does not allow the obtained structure to be used in the optical range due to the significant thickness (exceeding the surface roughness height) and the absorption coefficient of the carbon film in the optical range .

Layer-by-layer adsorption of charged polymer molecules (polyelectrolytes) is also widely used for the application of thin-film organic coatings at present. It allows you to apply both thin monolayers and create layered structures. It should be noted that polyelectrolyte molecules, due to the complexity of their structure and large sizes, can have several conformations. Different conformations lead to different thicknesses and roughness of the polymer coating (both single-layer and multi-layer).

A known method for the location of a polymer molecule that allows you to control its location on a substrate (see RF patent for the invention RU 2336124, IPC B01J 19/00, C12Q 1/68, B82B 3/00). The essence of the invention lies in the use of certain molecular interactions between a polymer molecule and a substrate. This allows you to both fix the conformation of the polymer molecule, and to move the molecule, or at least part of it, on the surface layer relative to the substrate by applying an external force followed by fixing the polymer molecule on the surface layer. Due to the configuration of the surface layer, it is possible not only to create elongated linear conformations of the molecules, but also to change the conformations in the desired way, as well as precisely place individual polymer molecules relative to other polymer molecules on the surface layer. Controlling the conformation of molecules and their position on the substrate allows you to set the minimum coating thickness.

However, obtaining a continuous organic coating by this method is difficult, since it involves technological operations with individual polymer molecules.

Closest to the proposed invention is a method for producing single or multilayer film elements by layer-by-layer adsorption, which consists in the deposition of polyionic molecules, that is, polymer molecules having an effective charge in solution, from a solution onto charged substrates (see patent US 5208111). The method includes modifying the substrate in such a way that negatively charged ions or ionizable negatively charged compounds are located over the entire surface area of the substrate, preparing an aqueous solution of polycationic molecules, adsorption of polycationic molecules onto a substrate, washing in deionized water and drying the substrate with a deposited layer in a stream of dry air. The charge of the first organic layer is opposite to the charge of the substrate. To precipitate the next layer, the substrate is placed in a solution with molecules having a charge opposite to the charge of the last deposited layer. This method allows to obtain organic coatings with high uniformity over large areas, while requiring low technological costs.

However, the thickness of the films obtained in this way can only be adjusted by using the method of stepwise layer-by-layer adsorption of material components in the process of material formation, that is, up to a thickness of 1 layer. The layer thickness difference arising from the deposition of polyelectrolyte molecules from a solution is not taken into account. In addition, the method adopted for the prototype does not allow adsorption to be controlled by external influences.

The objective of the invention and the technical result

The objective of the invention is to develop a manufacturing method by deposition from a solution of thin-film (nanometer) polymer coatings with a variable nanometer thickness and roughness comparable to the roughness of single-crystal semiconductor substrates.

The technical result consists in reducing the roughness and thickness of an organic coating consisting of these polycationic molecules.

SUMMARY OF THE INVENTION

The solution to this problem is achieved by first removing organic and inorganic contaminants from the surface of smooth single-crystal semiconductor substrates, creating an effective electrostatic charge on the surface of the substrates, adsorbing polyionic complexes from the solution onto the substrates by additionally illuminating the latter from the solution side with light with an optical wavelength from the intrinsic absorption region semiconductor substrate.

Description of drawings

The invention is illustrated by drawings, where figure 1 presents schematic images illustrating a change in the conformation of polyelectrolyte molecules at low (a) and high (b) surface charge densities of the substrate. Figure 2 shows the surface image of the silicon substrate after peroxide-ammonia treatment (a), the substrate with a layer of polyethyleneimine deposited when illuminated at a wavelength of 442 nm with an intensity of 8 mW / cm ² (b), and also without illumination (c), obtained using atomic force microscopy. Figure 3 illustrates the decrease in the thickness of the layer of organic coating of polyethyleneimine depending on the thickness of the "dark" coating when illuminating the substrate during adsorption (wavelength 442 nm, irradiation intensity 2 mW / cm ² ).

DETAILED DESCRIPTION OF THE INVENTION

For applying a thin-film organic coating by the method of layer-by-layer adsorption, it is necessary to use substrates whose surface has a charge. It is proposed to use single-crystal silicon wafers as substrates, since the charge of their surface can be changed using lighting due to the generation of electron-hole pairs in the surface layer. A change in surface charge can affect the conformation of the deposited polyelectrolyte molecules. A significant change in the conformation of molecules should lead to a change in the thickness and roughness of the deposited polyelectrolyte coating. Since the deposited polyelectrolyte layers have a nanometer thickness, the roughness of the initial substrates should be less than 1 nm.

First, the substrate, which is monocrystalline silicon with a layer of natural oxide, is cleaned and modified so that negatively charged ions or ionized negatively charged compounds are located over the entire surface area of the substrate. Preliminary preparation of silicon wafers included peroxide-ammonia treatment, leading to the removal of organic impurities and the creation of a negative charge on the surface due to the fixing (activation) of negatively charged OH groups. It consists in boiling at 75 ° C for 15 minutes in a solution of NH ₄ OH: H ₂ O ₂ : H ₂ O = 1: 1: 4. After boiling, the substrates were washed in deionized water for 20 minutes. The removal of natural silicon oxide was not carried out.

Since this method uses layer-by-layer deposition from a solution to precipitate the organic layer, deionized water and polymer molecules with an effective charge in the solution were used to create the solution. Adsorption occurs on silicon substrates with a negative charge, so cationic polyelectrolyte molecules (polyethyleneimine (PEI), polyamine, polyamidamine, polyacrylamide (PAA) and polychloride-diallyl-dimethyl-ammonium (PDADMAC, etc.) were chosen. These polyelectrolytes differ in molecular weight, degree of ionization in solution, and flexibility of macromolecules. The concentration of the aqueous solution of the polyelectrolyte can vary within wide limits. The adsorption time should be sufficient for the formation of a continuous coating on the substrate at the used concentrations and in practice is from 1 to 30 minutes.

The silicon substrate could be placed in the solution, or the solution was applied to its surface in the right place by capturing a certain amount of the solution with a pipette dispenser and then applying a drop to the right place on the substrate. In the latter case, it should be ensured that the solution does not evaporate during the adsorption period, for which it is necessary to maintain high humidity (more than 80%). This is ensured by placing the substrate in a sealed container made of a material that is transparent in the optical range (for example, glass). After the deposition process, it is necessary to rinse in deionized water and dry the obtained samples in a stream of dry nitrogen.

The illumination through the solution of that side of the substrate, where it is necessary to control the thickness and roughness of the polyelectrolyte deposited layer, is of decisive importance for achieving the claimed technical result. For lighting, you can use both monochromatic (including laser) and non-chromatic light sources (halogen lamp or incandescent lamp), however, quantitative assessment (forecasting) is possible only for monochromatic sources. In addition, the use of an incandescent lamp can lead to undesirable heating of the semiconductor substrate and the solution. The range of wavelengths used corresponded to the spectral sensitivity range of silicon (400-900 nm). It should be noted that water and most polyelectrolyte molecules do not absorb in the indicated range. The power of the light source (irradiation intensity), necessary to effectively change the thickness and roughness, depends both on the parameters of the polyelectrolyte molecules (degree of ionization of the polyelectrolyte molecules in the solution, the number of units in the molecule), and on the parameters of the silicon substrate (surface charge obtained during pretreatment , the degree of doping, the absorption coefficient, the rate of generation and recombination processes in the surface layer of a silicon substrate). Lighting leads to a decrease in the thickness and roughness of the deposited layers. The irradiation intensities necessary to achieve the minimum thicknesses and roughnesses of polycationic coatings were obtained experimentally. The obtained values of the irradiation intensity correlate with the estimate made taking into account the conformational dependence of molecules on the surface charge density of the substrate, proposed in [A.V.Dobrynin, A.Deshkovski, M.Rubinstein // Phys. Rev. Lett. 2000. Vol. 84. N.14. P.3101-3104].

In view of the foregoing, for single-crystal silicon substrates and monochromatic sources, the following formula can be used to estimate the quantum flux density Ф _cr , at which the reduction in thickness and roughness will be maximized:

см,

, q - заряд электрона [Кл], постоянная Больцмана [Дж/К], Т - температура раствора и кремниевой подложки [К], ε - диэлектрическая проницаемость кремния, ε₀ - диэлектрическая проницаемость вакуума [Ф/см], n_d - концентрация легирующей примеси [см^-3], n_i - собственная концентрация носителей заряда в кремнии [см^-3], s₁ - скорость поверхностной рекомбинации на лицевой стороне пластины [см/с], R - коэффициент отражения от поверхности кремния, а - длина связи в растворе, l_B=q²/ε_p-paε₀kT - длина Бьеррума [см], ε_р-ра - диэлектрическая проницаемость раствора, f - доля заряженных мономеров в молекуле, K - число мономеров в молекуле, N_ss - плотность отрицательно заряженных поверхностных состояний подложки [см^-2]. Откуда можно найти критическое значение интенсивности I_cr монохроматического света в зависимости от длины волны λ:Where

cm,

, q is the electron charge [C], the Boltzmann constant [J / K], T is the temperature of the solution and the silicon substrate [K], ε is the dielectric constant of silicon, ε ₀ is the dielectric constant of vacuum [F / cm], n _d is the concentration dopant [cm ^-3 ], n _i is the intrinsic concentration of charge carriers in silicon [cm ^-3 ], s ₁ is the surface recombination rate on the front side of the plate [cm / s], R is the reflection coefficient from the silicon surface, and is the length bonds in solution, l _B = q ² / ε _p-pa ε ₀ kT is the Bierrum length [cm], ε _p-pa is the dielectric constant of the solution, f is the fraction of the charge number of monomers in the molecule, K is the number of monomers in the molecule, N _ss is the density of negatively charged surface states of the substrate [cm ^-2 ]. Where can one find the critical value of the intensity I _{cr of} monochromatic light depending on the wavelength λ:

where h is the Planck constant [J · s], v is the radiation frequency [Hz], s is the speed of light [m / s].

The obtained result is explained by the fact that polycationic molecules adsorbed on a substrate create an uncompensated positive electric charge on the surface of silicon substrates, lighting generates nonequilibrium electron-hole pairs in the surface layer of the substrates, the concentration of which depends on the light intensity, and nonequilibrium charge carriers can not only compensate the surface charge, but even with sufficient illumination intensity, nonequilibrium electrons from the near-surface layer along a semiconductor tunnel through the surface oxidized layer, increasing the negative charge on the surface of the structure and, accordingly, the electrostatic attraction of polycationic molecules. This leads to a change in the conformation of the deposited polyelectrolyte molecules in accordance with figure 1, which leads to a decrease in the thickness of the organic coating, consisting of polycationic molecules (photosorption effect), and its roughness. For the quantitative characterization of the photosorption effect, the formula

where D _ill and D _d are the thicknesses of the adsorbed layers under lighting and in darkness, respectively.

Measurements of the morphology of the surface of the coatings carried out using atomic force microscopy (Fig.2), and the thickness of the coatings made using ellipsometry (Fig.3), confirmed the above reasoning. It should be noted that the described photosorption effect is not associated with a decrease in the number of adsorbed molecules under illumination, the magnitude of the photosorption effect shown in Fig. 3 increases in absolute value with an increase in the thickness of the deposited dark layer, and the effect itself is always negative, i.e., lighting leads to a decrease in the thickness regardless of the type of conductivity of the substrate, which is not typical for the mechanisms described in [Baru V.G., Volkenstein F.F. The effect of irradiation on the surface properties of semiconductors. - M .: Nauka, 1978. - 288 p.], That is, it cannot be explained by the desorption of molecules upon illumination of the substrate.

Case Studies

Example 1

The initial substrate is n-Si (100) with a specific resistance of 3-6 Ohm · cm and a roughness of 0.8 A.

The substrates were treated for 15 minutes in an ammonia peroxide solution of NH ₄ OH: H ₂ O ₂ : H ₂ O = 1: 1: 4 at 75 ° C.

An aqueous solution of polyethyleneimine (-C ₂ H ₅ N-) _x was prepared with a molecular weight of 25 kDa and a concentration of 1 mg / ml polyelectrolyte in deionized water with a specific resistance of 18 MOhm · cm. Estimating the number of fragments of the PEI molecule by dividing the molecular weight of the PEI by the molecular weight of the unit gives a value of the order of 600.

The substrate was immersed in a solution of polyelectrolyte. The adsorption time varied from 1 to 60 minutes (Table 1). To illuminate the substrate, a He-Cd laser with a wavelength of 442 nm and a radiation intensity of 2 mW / cm ^{2 was used} . To minimize errors, the magnitude of the effect was calculated for samples obtained during one experiment (deposition), and one of the samples was illuminated.

After adsorption, the samples were washed for 10 minutes in deionized water with a specific resistance of 18 MOhm · cm and dried in a stream of dry nitrogen.

To measure the thickness of the coatings, a Multiscop ellipsometer from Optrel (Germany) with a He-Ne laser (λ = 632.8 nm) was used. Based on the refractive indices of the studied objects (silicon with a layer of natural oxide about 2 nm thick, as well as nanometer organic coatings), which lie in the range n = 1.4-1.5, a laser beam angle of 70 ° was chosen for measurements . Since this value is close to the Brewster angle for these materials, this made it possible to increase the accuracy of measurements. Also, to increase the accuracy and reliability of the results, a series of measurements of the substrates was carried out before applying a layer of polyethyleneimine and immediately after application. The layer thicknesses were found by solving the direct ellipsometry problem for the case with two interfaces (air / silicon oxide / silicon substrate) and three (air / polyelectrolyte layer / silicon oxide / silicon substrate) interfaces. For the calculation, we used the values of refractive indices (n) and extinction (k): for silicon - 3.88858 and 0.02, respectively; for silicon oxide -1.4598 and 0; for air - 1 and 0; for polyethyleneimine - 1.453 and 0. The calculated values of the layer thicknesses were averaged over at least 3 measurements in different areas of each sample, with a maximum variation of values of less than 1 A. For AFM measurements, the NTGRA-Spectra probe nanolaboratory (NT-MDT, Russia). Scanning was carried out with a frequency of 0.3-0.5 Hz in the tapping mode in air using a NSGll / Pt cantilever (NT-MDT) with platinum spraying. The results are shown in table 1 and figure 2.

Table 1 - Dependence of the thickness of the adsorbed PEI layer and the surface roughness of the structure coating on the adsorption time carried out without illumination and at fixed illumination (with a wavelength of 442 nm and a radiation intensity of 2 mW / cm ² ) Adsorption time, min The thickness of the layer of polyethylenimine, precipitated without lighting, And The thickness of the layer of polyethyleneimine precipitated by lighting, And The surface roughness of the structure obtained without lighting, And The surface roughness of the structure obtained by lighting, And one 7.0 ± 0.5 5.0 ± 0.5 1,5 1,0 3 8.0 ± 0.5 5.5 ± 0.5 2,5 1,0 5 12.0 ± 0.5 8.5 ± 0.5 3,5 2,5 10 9.0 ± 0.5 6.0 ± 0.5 2,5 1,0 twenty 7.0 ± 0.5 5.0 ± 0.5 1,5 1,0 thirty 6.5 ± 0.5 5.0 ± 0.5 1,5 1,0 60 6.0 ± 0.5 5.0 ± 0.5 1,5 1,0

Thus, the maximum decrease in the thickness (by 33%) and roughness (by 60%) of the polyethyleneimine layer obtained in 10 minutes of adsorption on n-type silicon was obtained under illumination with a wavelength of 442 nm and a radiation intensity of 2 mW / cm ² .

Example 2

The original substrate was used — p-Si (100) with a specific resistance of 9 Ohm · cm and a roughness of 0.8 A. Pretreatment of the substrates, preparation of a PEI solution, the steps of the deposition of the polyelectrolyte layer, washing and drying also coincided with Example 1. The characterization methods also coincided . The results are shown in table 2 and figure 3.

Table 2 - Dependence of the thickness of the adsorbed PEI layer and the surface roughness of the structure coating on the adsorption time carried out without illumination and at fixed illumination (with a wavelength of 442 nm and a radiation intensity of 2 mW / cm ² ) Adsorption time, min The thickness of the layer of polyethylenimine, precipitated without lighting, And The thickness of the layer of polyethyleneimine precipitated by lighting, And The surface roughness of the structure obtained without lighting, And The surface roughness of the structure obtained by lighting, And one 7.5 ± 0.5 6.0 ± 0.5 1,5 1,0 3 9.0 ± 0.5 6.5 ± 0.5 2,5 1,0 5 13.0 ± 0.5 9.5 ± 0.5 3,5 2,5 10 10.0 ± 0.5 7.0 ± 0.5 2,5 1,5 twenty 8.0 ± 0.5 6.0 ± 0.5 1,5 1,0 thirty 7.5 ± 0.5 6.0 ± 0.5 1,5 1,0 60 7.0 ± 0.5 6.0 ± 0.5 1,5 1,0

Thus, the maximum decrease in the thickness (by 30%) and roughness (by 60%) of the polyethyleneimine layer obtained in 10 minutes of adsorption on n-type silicon was obtained under illumination with a wavelength of 442 nm and a radiation intensity of 2 mW / cm ² .

Example 3

We used substrates and solutions for the deposition of the polyelectrolyte layer described in Example 1. Pretreatment of the substrate, washing and drying steps also coincide with Example 1. Polyethyleneimine was adsorbed onto a silicon substrate under the following conditions:

The substrate was immersed in a solution of polyelectrolyte, the adsorption time of 5 minutes. To illuminate the substrate, a He-Cd laser with a wavelength of 442 nm was used, the radiation intensity of which was varied using a polarizer and a half-wave plate from 1 to 30 mW / cm ² . The results are presented in table.3.

Table 3 - Dependence of the thickness and roughness of the adsorbed layer of polyethyleneimine on the intensity of illumination of the surface of an n-Si laser with a wavelength of 442 nm The intensity of lighting, mW / cm ² The thickness of the layer of polyethyleneimine precipitated by lighting, And The surface roughness of the structure obtained by lighting, And 0 Without cover 0.8 0 12.0 ± 0.5 3,5 one 9.0 ± 0.5 2.5 2 8.5 ± 0.5 2,5 four 7.5 ± 0.5 1,5 8 5.0 ± 0.5 1,0 fifteen 5.0 ± 0.5 1,0 thirty 5.0 ± 0.5 1,0

Thus, the maximum decrease in thickness (by 58%) and roughness (by 71%) of the layer of polyethyleneimine deposited in 5 minutes was obtained already at an illumination intensity of 8 mW / cm ² and does not increase with a further increase in intensity.

Example 4

We used substrates and solutions for the deposition of the polyelectrolyte layer described in Example 1. Pretreatment of the substrate, washing and drying steps also coincide with Example 1. The PEI deposition algorithm for illumination is similar to Example 3 with the only difference being that a solid-state laser with a wavelength of 650 nm was used , the radiation intensity of which was varied using a polarizer and a half-wave plate from 1 to 30 mW / cm ² . The results are presented in table 4.

Table 4 - Dependence of the thickness and roughness of the adsorbed layer of polyethyleneimine on the intensity of illumination of the surface of an n-Si laser with a wavelength of 650 nm The intensity of lighting, mW / cm ² The thickness of the layer of polyethyleneimine precipitated by lighting, And The surface roughness of the structure obtained by lighting, And 0 Without cover 0.8 0 12.0 ± 0.5 3,5 one 8.5 ± 0.5 2.0 2 7.5 ± 0.5 1,5 four 5.0 ± 0.5 1,0 8 5.0 ± 0.5 1,0 fifteen 5.0 ± 0.5 1,0 thirty 5.0 ± 0.5 1,0

Thus, the maximum decrease in thickness (by 58%) and roughness (by 71%) of the polyethyleneimine layer deposited in 5 minutes was obtained already at an illumination intensity of 4 mW / cm ² and does not increase with a further increase in intensity.

Example 5

The source substrates and their pre-treatment are the same as Example. one.

An aqueous solution of polychloride diallyl-dimethyl-ammonium PDADMAC was prepared. (-C ₈ H ₁₆ ClN-) _x with a molecular weight of 200-350 kDa and a concentration of 1 mg / ml polyelectrolyte in deionized water with a specific resistance of 18 MOhm · cm. Estimation of the number of fragments of the PDADMAC molecule by dividing the molecular weight of PDADMAC by the molecular weight of the unit gives a value of the order of 1250-2150.

The stages of deposition of the polyelectrolyte layer, washing and drying also coincide with Example 1. Characterization methods also coincide.

Table 5 - Dependence of the thickness of the adsorbed PDADMAC layer and surface roughness of the structure coating on the adsorption time carried out without illumination and at fixed illumination (with a wavelength of 442 nm and an radiation intensity of 2 mW / cm ² ) Adsorption time, min The thickness of the layer of PDADMAC, precipitated without lighting, And The thickness of the layer of PDADMAC, precipitated by lighting, And The surface roughness of the structure obtained without lighting, And The surface roughness of the structure obtained by lighting, And one 10.0 ± 0.5 6.5 ± 0.5 3.0 1,0 3 11.0 ± 0.5 7.5 ± 0.5 3.0 1,5 5 16.0 ± 0.5 10.5 ± 0.5 4.0 3.0 10 12.0 ± 0.5 8.0 ± 0.5 3,5 2.0 twenty 10.0 ± 0.5 6.5 ± 0.5 3.0 1,0 thirty 8.5 ± 0.5 6.5 ± 0.5 2,5 1,0 60 8.0 ± 0.5 6.5 ± 0.5 2,5 1,0

Thus, the maximum decrease in the thickness (by 35%) and roughness (by 66%) of the PDADMAC layer obtained after 20 minutes of adsorption on n-type silicon was obtained under illumination with a wavelength of 442 nm and a radiation intensity of 2 mW / cm ² .

Claims (3)

1. A method of manufacturing a thin film organic coating of a cationic polyelectrolyte, including modifying the substrate to create an effective negative electrostatic charge, preparing an aqueous solution of the cationic polyelectrolyte, adsorption of the cationic polyelectrolyte on the substrate, washing in deionized water and drying the substrate with a deposited layer in a stream of dry air, characterized in that monocrystalline silicon with a roughness less than or comparable to the thickness is used as the substrate emogo coating modifying a silicon substrate for an effective negative electrostatic charges is performed by boiling at 75 ° C for 15 minutes in a solution of NH ₄ OH: H ₂ O _2: H ₂ O = 1: 1: 4, and during adsorption of the cationic polyelectrolyte to the substrate illuminates the substrate from the solution side with light with an intensity in the range of 2 mW / cm ² -8 mW / cm ² and with wavelengths from the intrinsic absorption region of silicon. 2. The method according to claim 1, characterized in that the adsorption is carried out by immersing the silicon substrate in an aqueous solution of a cationic polyelectrolyte. 3. The method according to claim 1, characterized in that the adsorption is carried out by applying a drop of an aqueous solution of cationic polyelectrolyte to the desired location on the surface of the silicon substrate using a pipette dispenser.

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